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Looking to play with my bikes fit over the couple of rides, lowering the stem a little... Can I safely run multiple spacers on top of the stem before deciding to cut the steerer down any further?Currently the steerer is cut to run 30mm spacers under stem with a 5mm one on top.Chris King 1 1/8 no threadset.ENVE 2.0 forks + Compression plug.Thomson Stem.

Not necessarily; some forks really need a compression plug to help support/resist the clamping force of the stem, rather than just being there for preloading the headset. Not sure if this is the case with this Enve fork, but keep in mind that putting spacers on the top of the stem means the compression plug will now be 'above' the stem rather than 'in line' with the stem.

I couldn't see anything about max. spacers on top of the stem - I'll check again in the morning though. I read the 1mm steerer above stem and 5mm spacer on top. And a max. of 40mm spacers between headset and base of stem.

Your fine. No need to crank down on the stem clamp so tight that you need reinforcement inside the steer tube to keep it from crushing. Those Thomson stems don't need much force to keep them put anyways.

Last edited by bricky21 on Fri Feb 15, 2013 2:25 am, edited 1 time in total.

The reason of HakeemT's point is that without proper inner support a light steerer tube often comes with a thin wall which is easily ovalised (if not destroyed) by the pressure exerted by the stem's fixing screws. Hence his suggestion for the use of a T-shaped bung/topcap that runs from the top of the steerer tube all the way down to the expander proper which is then placed in the area where to lower fixing screw of the stem is.A not so common system that works well provided the steerer is either cut to precise length to accomodate the T-shaped device which also precludes the use of spacers on top of the stem.

If a long enough expander is used and sits inbetween the fixing screws then no damaging compression could occur. Not sure such a device exist. I doubt it.Another solution and I feel one that works very well is to use carbon mounting paste between the steerer tube and the stem i.e. put on the outside of the steerer tube which allows to reduce torque on the stem bolts by about 30% which in turn should be low enough so the steerer tube is not ovalised or prone to crushing damage.

In all cases work with the utmost care so the steerer is not damaged. Best to use a torque wrench and go easy on the torque you apply. With carbon paste applied to the tube the chance of twisting or lifting the stem clear off the steerer tube is virtulally non-existant for road use.

Wouldn't the unsupported section of steerer between the stem and the top headset bearing be subject to higher forces when riding than the 5-6 nm clamping the stem? Particularly right at the bottom of the stem clamp, and at the top of the bearing.

Point is, that if a steerer really needed reinforcement from small deformations wouldn't that reinforcement have to extend from the top of the stem to below the top bearing of the headset to truly be effective?

iamalex wrote:I couldn't see anything about max. spacers on top of the stem - I'll check again in the morning though. I read the 1mm steerer above stem and 5mm spacer on top. And a max. of 40mm spacers between headset and base of stem.

And fa63, that looks like a fairly common length for an expander; keep in mind that running 40mm of spacers above a stem means you'd need close to 80mm of expander length (i.e spacers + stem stack which often (not always) ends up being in the 40-45mm region); I doubt that the expander pictured is that long.

That being said, as long as it is for fitting purposes only I think you will be OK with running a couple of spacers above the stem for a short amount of time and while doing easy riding. Keep in mind though that 40mm is a big range so if you're that unsure about your position it may take a while longer to dial in the right stem height...

I believe that expander is about ~50 mm long, so it is a bit longer than other expanders I have used and would provide full support once the fork is cut to size. That said, you are right about it not providing full support if you have a bunch of spacers stacked over the stem.

Most forks allow the use of spacers on top of a stem for a limited amount of time before finally cutting it down. Specialized mentions this specifically. Maybe Cannondale too, I cant remember. Similarly, 3t forks say that their glued insert is optional, but increases their tolerance for mishandling. So you're fine. just cut it down when you're confident of where you want your stem to be.